An In-Depth Study of Staphylooccus aureus Infections and Cases of Colonization in the Inpatient Population at a University Teaching Hospital

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen that has historically been identified in hospital-acquired infections since the mid 1900\u27s. Epidemiologically significant trends have occurred which have identified the increasing prevalence of MRSA in the community setting. Methods: An investigation of all isolates positive for Staphylococcus aureus of the inpatient population was conducted over a nine year time period in a university teaching hospital. Additionally, a unit specific case/control study was conducted during an outbreak of MRSA in a neonatal intensive care unit. Results: From January of 1997 through December of 2005, the number of isolates identified as positive for S. aureus had increased. Additionally, the proportion of MRSA to Methicillin-sensitive Staphylococcus aureus (MSSA) had increased from 40 to 60%. A chi-square test was conducted comparing the number of isolates positive for MRSA in 1997 versus 2005 which was found to be statistically significant with a P value \u3c 0. 001. Additionally, from January 1997 through December 31, 2001, the first greatest change in proportion of MRSA to MSSA was noted. The increase in isolates identified as positive for MRSA was found to be approximately three times as great. The comparison of isolates identified as MRSA in 1997 versus 2001 was statistically significant with a P value \u3c0.001. A hospital-acquired case is defined as one in which the specimen positive for MSSA or MRSA was obtained 48 hours after admission to the hospital. Conversely, a community-acquired case is defined as having a culture positive for MSSA or MRSA obtained within 48 hours of admission. Using a chi-square test we found no statistically significant difference in identification of the acquisition of MSSA or MRSA as to whether the patients were adrnitted from home or another health care institution. The number of community-acquired cases identified as positive for MRSA was higher than those that were hospitalacquired. Lastly, through a case/control study of infants leading to NlCU employee screening for identification of employees for positive colonization status with MRSA, we identified the common source who served as a reservoir for transmission of this pathogen. Conclusion: Methicillin-resistant Staphylococcus aureus has emerged as a significant public health burden and serves as a warning requiring the attention of key stakeholders to implement rigorous actions to control the spread and reduce the development of multi-drug resistant organisms